Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$127.33	11.262%	$141.6699	$141.67	$141.65	$141.70
Purchase #2	$19.76	4.622%	$20.6733	$20.67	$20.65	$20.70
Purchase #3	$117.89	10.675%	$130.4748	$130.47	$130.45	$130.50
Purchase #4	$128.75	10.669%	$142.4863	$142.49	$142.50	$142.50
Purchase #5	$68.39	13.266%	$77.4626	$77.46	$77.45	$77.50
Purchase #6	$109.97	10.695%	$121.7313	$121.73	$121.75	$121.70
Purchase #7	$73.79	13.201%	$83.531	$83.53	$83.55	$83.50
7 purchase totals =	$645.88		$718.0292	$718.02	$718.00	$718.10